LSD 1-2003
A NEMA Lighting Systems Division Document
Tungsten-halogen Lamps (Bulbs):
Ultraviolet, Rupture,
And High Temperature Risks
Prepared by
Lamp Section
National Electrical Manufacturers Association
th
1300 North 17 Street, Suite 1847
Rosslyn, Virginia 22209
January 4, 1999
Revised July 21, 2003 (v2.4)
The requirements or guidelines presented in this document, a NEMA Lighting Systems Division white paper, are
considered technically sound at the time they are approved for publication. They are not a substitute for a product seller’s
or user’s own judgment with respect to the particular product(s) discussed, and NEMA does not undertake to guarantee
the performance of any individual manufacturer’s products by virtue of this document or guide. Thus, NEMA expressly
disclaims any responsibility for damages arising from the use, application, or reliance by others on the information
contained in these white papers, standards, or guidelines by others.
LSD 1-2003
Contents
Foreword ................................................................................................................... 3
Tungsten-halogen Lamp Basics (Operation)............................................................. 3
Potential Risks........................................................................................................... 4
Ultraviolet Radiation ........................................................................................ 4
Lamp Rupture................................................................................................... 5
High Temperature ............................................................................................ 5
Luminaire Safety Standards ...................................................................................... 5
Lamp Labeling .......................................................................................................... 6
Conclusion................................................................................................................. 7
Exhibits
A
B
C
Cautionary Notice ............................................................................................ 8
Safety Tips........................................................................................................ 9
Crossed-through Torchiere............................................................................... 10
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LSD 1-2003
Tungsten-halogen Lamps (Bulbs)1
Ultraviolet, Rupture, and High Temperature Risks
Foreword
Periodically, concern is expressed about the risks associated with the use of
tungsten-halogen lamps. The US lamp industry was at the forefront of these risk
assessments and initiated the development of American National Standard ANSI
C78.1451, Use of Protective Shields with Tungsten-halogen Lamps--Cautionary Notice,
addressing requirements for safe use of these lamps. The U.S. lamp industry has also
participated in the development of an international IEC safety standard for lamps. This
international standard has been adopted by ANSI.2 Much of the concern is due to a lack
of awareness of appropriate safety standards for both lamps and luminaires.
This document summarizes the benefits and the safe operation of tungstenhalogen lamps.
Tungsten-halogen Lamp Basics (Operation)
Tungsten-halogen lamps were introduced in the 1960s and have been developed
for use in many applications previously served by incandescent lamps. Ordinary
incandescent lamps darken over life due to the evaporation of tungsten from the filament
that condenses on the cool glass wall. To reduce this darkening and to increase life, a
halogen, such as iodine or bromine, is added to the filling gas of tungsten-halogen lamps.
During lamp operation, evaporating tungsten chemically combines with the halogen gas
near the bulb wall. The tungsten is then re-deposited back on the filament, and the
halogen gas is released to repeat the cycle. Because the bulb is typically pressurized and
the bulb wall temperature must exceed 250o C to maintain effective operation of the
halogen cycle, a strong, small diameter, quartz or hard glass tube is used. Compared to
1
The lamp industry uses the term “lamp” for the light source, for what the consumer may refer to as a
“bulb.” Throughout this document, lamp is used for the light source.
2
IEC Publication 60432-2 (1999-10), Safety Specifications for Incandescent Lamps--Part 2: Tungstenhalogen Lamps for Domestic and Similar General Lighting Purposes.
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LSD 1-2003
ordinary incandescent lamps of the same wattage, tungsten-halogen lamps maintain their
initial light output over their full life, and lamp life can be increased by more than 100
percent.
Potential Risks
Three risks associated with improperly used tungsten-halogen lamps are (1) overexposure to ultraviolet [UV] radiation, (2) the consequences of lamp rupture, and (3) the
consequences of high operating temperatures.
Ultraviolet Radiation
The light output characteristics of tungsten-halogen lamps are qualitatively
similar to those of ordinary incandescent lamps. Most of the radiated energy is in the
infrared spectral region, much less is in the visible region, and less than 1 percent is in
the ultraviolet band. In a regular incandescent lamp, the glass envelope absorbs almost
all of this ultraviolet radiation. In tungsten-halogen lamps manufactured with a standard
quartz capsule, the quartz absorbs little of the ultraviolet radiation. Thus, transmission of
the small amount of ultraviolet energy may result in UV over-exposure if these lamps are
used in an unshielded fixture, at close range, and for an extended period of time. Overexposure to UV radiation from lamps may cause skin and eye irritations, exactly as it
may for over-exposure to the sun.
Many tungsten-halogen lamps are available using materials that absorb UV. The
use of hard glass for the capsule in some tungsten-halogen lamps provides a good
protective shield against the transmission of the ultraviolet energy, as in an ordinary
incandescent lamp. Lamps are also now available that use a capsule that is made with a
special quartz, which is doped to selectively absorb the UV wavelengths while passing
the visible light. Other lamp types have an outer glass jacket which offers protection
against UV transmission.
All NEMA lamp manufacturers provide cautionary notices regarding exposure to
ultraviolet radiation (for example, Exhibit A), if necessary for a particular lamp.
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LSD 1-2003
Lamp Rupture
Both quartz and hard glass tungsten-halogen bulbs are pressurized for proper
operation. Consequently, should the lamp envelope break, particles of extremely hot
glass could be discharged.
Lamp manufacturers recommend that some tungsten-halogen lamps be used in
luminaires with suitable shielding to protect against the risk of shattering. NEMA
manufacturers always provide a cautionary notice with lamps having this requirement
(for example, Exhibit A).
Some tungsten-halogen lamps are designed and manufactured such that luminaire
shielding against shatter is not required. These lamps can be found in several styles.
Examples of lamps that may not require shielding are 12-volt low-pressure lamps, lamps
with G9 bases, or lamps with an outer glass jacket. Always read the information supplied
with a lamp to determine if shielding is required by the lamp manufacturer. However,
shielding could still be required by the UL luminaire standards.
Lamp rupture is more likely for lamps that are not manufactured in accordance
with IEC safety standards or other proven quality control procedures.
High Temperature
The bulb wall temperature of the halogen capsule must exceed 250o C (480o F) for
proper operation of the lamp. Depending on the bulb diameter and lamp wattage, the
bulb wall temperature may approach 650o C (1200o F). Tungsten-halogen lamps must
always be used in an appropriate luminaire and in an application that will prevent the
accidental contact of combustible materials with the bulb wall or other hot surfaces.
Also use caution and allow enough time for the lamp to cool before attempting
replacement.
Luminaire Safety Standards
The lamp industry has worked with Underwriters Laboratories (UL) to establish
requirements for luminaires using tungsten-halogen lamps. Refer to UL 1598 and UL
153.
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LSD 1-2003
In the past consumers placed tungsten-halogen luminaires, especially torchiere
types, near combustibles, such as curtains, that could come into contact with hot surfaces,
increasing the risk of fire. UL revised its safety standard UL 1533 to include a tungstenhalogen abnormal operation test to minimize this risk. Also, the current UL lighting
warning notice advises users to keep the luminaire away from curtains and other
combustible materials. See Exhibit B for a list of specific safety tips for application of
halogen torchiere luminaires that has been released by UL.
Temporary halogen lighting, where luminaires are often not securely or
permanently fastened to a structure, may require additional precautions. There have been
reports that stem-type fixtures, which are normally fastened to an exhibit booth with
mechanical clamps, can, if the clamp becomes loose, swing out of position and place the
hot luminaire or cover glass in close proximity to combustible materials. Such
applications require careful assembly of the lighting equipment. This temporary lighting
should not be left unattended. Temporary halogen lighting equipment should also be
carefully maintained, using only the original manufacturer’s replacement components.
Lamp Labeling
In the mid-1980s, the lamp industry developed a cautionary notice for the use of
tungsten-halogen lamps that was first published in American National Standard C78.1451
in 1988. Exhibit A is a typical caution notice used by manufacturers based on
information provided in C78.1451.
In addition ANSI C78.260, Tubular Tungsten-halogen Lamps--Physical
Characteristics, has been revised to include a section on lamp marking. This section
requires, for 500 watt, double-ended halogen lamps ONLY, that the lamp manufacturers
add a warning statement on the front panel of the card or other package displaying these
products for retail sale. If space is available, a pictogram of a crossed through torchiere
fixture is also to be incorporated with the warning statement. This additional marking
was initiated at the request of the Consumer Product Safety Commission to warn
consumers that 500 watt lamps are not for use in indoor residential lighting fixtures. See
the figure in Exhibit C.
3
UL 153, Safety Standard for Portable Electric Luminaires.
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Conclusion
Long-term industry experience indicates that the use of tungsten-halogen lamps does
not pose a hazard when used with a properly designed luminaire in accordance with lamp
manufacturers’ recommendations. Requirements such as shielding are not the same for
all tungsten-halogen products. Always read and heed the manufacturer’s warnings and
instructions that are supplied with the lamp and luminaire.
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Exhibit A
Cautionary Notice
Caution: This lamp operates under pressure and produces intense heat. It
also generates a slight amount of UV radiation. Therefore, the lamp must be
used in a fixture that has a suitable glass or plastic shield to protect against the
risk of lamp shattering and UV exposure.
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LSD 1-2003
Exhibit B
Safety Tips
The following excerpt is taken from a July 29, 1996 UL Press Release that summarizes safety
tips for the users of portable lamp fixtures.
To reduce risk of fire and injury in your home, UL offers the following precautionary measures to
follow with all portable lamps:
•
Look for the UL Mark when purchasing portable lamps.
The UL Mark means that
representative samples of the product have been tested to and have met UL’s Standards for
Safety.
•
Read the manufacturer’s use and care instructions before using portable lamps anywhere in
the home. Pay special attention to warning labels. Portable lamps are intended for indoor
use only, unless marked otherwise.
•
Always turn off or unplug the lamp before removing or replacing bulbs.
•
Never attempt to replace or discard a bulb that is hot to the touch.
•
Never use a light bulb of a different style or higher wattage than indicated by the
manufacturer’s use and care instructions.
•
Never operate a lamp with missing or damaged components.
•
Never place materials on the top of a lamp, such as clothes or towels.
•
Never place lamps in locations where they can be easily tipped over by children or pets.
•
Never use torchiere lamps in children’s bedrooms or playrooms. Children may play with the
lamps or unknowingly place combustibles, such as stuffed toys or clothing, too close to the
bulb area.
•
Keep torchiere lamps away from elevated beds, such as bunk beds, where bedding may get
too close to the bulb area.
The U.S. Consumer Product Safety Commission released similar safety tips via a July 29, 1996
Press Release (CPSC #96-174). For more information on halogen fixture safety, contact either
UL at 847-272-8800 or the U.S. Consumer Product Safety Commission at 301-504-0580,
Extension 1166.
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LSD 1-2003
Exhibit C
Crossed-through Torchiere
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